DYNAMIC ANALYSIS OF STEEL ARCH BRIDGES

Abstract

Arch bridges are one of the oldest types of bridges having great natural strength. The weight is transferred to the supports at each end. These supports, called abutments carry the load and keep the ends of the bridge from spreading out. In this study an attempt has been made to present dynamic analysis of steel arch bridges and their characteristics in both the longitudinal and transverse directions under different load conditions. The bridges have been considered as a trussed arch with steel boxes consists of different cross-sectional area to make the bridge safe with design as well as economic aspects. Trussed system has been considered as no bending moment acts on the structure. The location of the bridges considered over a deep gorge, which is not only strategic area but also prone to earthquake with high wind velocity. For that critical location, it would have been difficult to control transverse displacements due to wind and earthquake in any other type of bridges. This is why trussed arch system have been considered. It is observed that the seismic response is relatively smaller when subjected to longitudinal excitation, but significantly large under the transverse ground motion. The force for combine dead load + earthquake load is smaller as compared to dead load + half live load. Therefore the combination of dead load and half span live load condition is most critical condition. This happens due to unsymmetrical loading on arch system. It also has been observed that three arch bridge system is more stiff than two arch bridge system.